Delaying weaning and adopting a stepped-down approach can reduce problems at weaning by improving the transition from a monogastric calf to a young ruminant.
The latest findings from research carried out by Trouw Nutrition into calf nutrition and growth which follows calves through into the milking herd shows weaning management plays a key role in calf development, especially in calves fed on elevated levels of milk replacer.
Ruminant technical manager Georgina Thomas says: “The new research focuses on how the rumen develops. At weaning major changes occur in the calf’s digestive system as they move from being effectively a monogastric to a functioning ruminant. How calves are weaned affects how the rumen and gastrointestinal tract develops, which impacts on growth and also the incidence of scours.”
She explains in the pre-weaned calf the rumen is under-developed with very small papillae, as most digestion occurs in the abomasum. Post-weaning there is a rapid increase in the growth and absorptive capacity of the rumen.
“The rumen moves from being 30 per cent of the intestinal tract to 70 per cent. It must develop to optimise the absorption of volatile fatty acids, which are produced. In addition, the digestive system has a secondary role in helping prevent micro-organisms, which can potentially cause scours and ill health, from entering the blood stream – it has an important barrier function.
“In simple terms, the older the calf is weaned the less permeable the digestive tract and the better developed the rumen can be, which combined can help prevent post-weaning growth checks and also help reduce the risk of scours at what is a stressful time for the animal.”
Ms Thomas says as the process of weaning results in milk being removed from the calf’s diet, it is important to stimulate development of the rumen by increasing starter feed to maintain total energy intakes. If milk intakes are reduced and the rumen has not been adequately developed the consequences will be a growth rate check and an increased risk of scours.
“Trials comparing step-down weaning with abrupt weaning approaches showed that with step-down weaning over a two-week period starting at six weeks the intake of starter feed increased more quickly than on an abrupt system, and as a result growth rate checks were less pronounced.”
Comparing eight-week-old and six-week-old weaning on a step-down system, she says the older calves were better placed to maintain total energy intakes, compensating for reduced milk powder levels intakes by increasing both solid feed intakes. Younger calves experienced a more significant drop in energy intakes.
“As the principles of rumen development are the same whatever the rate of milk powder use, dairy farmers should consider delaying weaning and using the step-down approach to minimise growth rate checks and the risk of scours,” Ms Thomas advises.